For purposes of the present application, an imitation cheese is defined as those cheese-like products wherein at least part of the fat is a non-milk fat and wherein the solids are at least partially derived from acid or rennet casein or caseinates. These products may contain some non-fat milk solids and some milk fat. Imitation cheese products are made by a process wherein the ingredients are emulsified and pasteurized. In a typical process for the preparation of imitation cheese products, acid or rennet casein or a caseinate salt (either calcium or sodium caseinate) is blended with a liquid vegetable oil in a ribbon blender. The caseinate/liquid oil blend is then added to a lay down cooker and any water required is added along with any emulsifier salts which are to be used. Heat and agitation are then used to solubilize the casein. The usual temperature range of heating is 165.degree. F. to 195.degree. F. A homogeneous plastic mass, much like process cheese, is formed during the heating and agitation steps. The homogeneous plastic mass is discharged from the lay down cooker in accordance with usual process cheese making procedures.
Casein can be separated from the whey proteins of skim milk by acid precipitation at pH 4.3-4.6 and by coagulation with rennet, or other proteolytic enzymes. In the preparation of acid casein, skim milk is cultured with lactic acid-producing organisms, usually streptococcus lactic or streptococcus cremoris, until it coagulates at pH 4.3-4.6, which is the isoelectric pH of the casein complex. The coagulum is broken and heated to about 120.degree. F. to expel whey, is thoroughly washed, pressed, ground, dried and milled. Alternatively, lactic acid, hydrochloric acid or sulphuric acid may be added directly to agitated skim milk until the desired pH is attained. The temperature is raised to 110.degree.-115.degree. F. to enhance precipitation of the casein, which is collected and processed. Acid casein is usually designated according to the acid utilized in its production, such as lactic casein, hydrochloric acid casein or sulphuric acid casein. Acid caseins are insoluble unless the pH is adjusted with a suitable base to provide an alkali or alkaline earth caseinate.
When rennet is added to skim milk, colloidal casein is destabilized and forms a gel. Sufficient rennet and calcium chloride is added to skim milk at about 85.degree. F. to yield a coagulum in twenty to thirty minutes. Agitation is initiated following the onset of coagulation to reduce the particle size and to optimize processing. After raising the temperature to 130.degree. F. to 150.degree. F. to expel whey, the curd is collected and processed. Rennet casein is also insoluble.
Both acid casein and rennet casein have long been used in the manufacture of imitation cheese. Problems arise, however, when acid casein or rennet casein is stored for any substantial period of time prior to use. As indicated above, acid casein and rennet casein are usually dried prior to storage and in the dried form usually contain about 10% to 12% moisture. Stale and off flavors can rapidly occur if the storage conditions for acid casein and rennet casein are not optimum, i.e., if stored at relatively high temperature or at relatively high humidity conditions.
U.S. Pat. No. 4,197,322 to Middleton recognizes the problem of stale flavors in acid casein which is to be used in the manufacture of imitation cheese. The Middleton patent is directed to a method for removing the off flavors from acid casein, prior to using the casein to produce an imitation cheese. In the process of the Middleton patent for producing an imitation cheese, an aqueous suspension of acid casein containing undersirable flavor and odor elements is formed into an aqueous suspension having a solids content of from about 3% to about 15%. The acid casein is reacted with a basic calcium salt and a neutral calcium salt to form a calcium caseinate solution essentially free of observable solids. This is in accordance with standard methods for producing caseinates which is achieved by the slow addition of a suitable alkali to a suspension of insoluble acid casein. In the method of the Middleton patent the calcium caseinate solution is adjusted in pH to from about 5.9 and 6.9 by the addition of an acid. Thereafter, rennet is added to the solution of calcium caseinate to form a rennet curd in a supernate aqueous solution. The rennet curd is separated from the aqueous portion which contains the undesirable odor and flavor elements present in the original acid casein. The rennet curd is mixed with an edible oil, salt and an edible emulsifying agent at a temperature of about 140.degree. F. to produce a smooth admixture. An acid is then added to the admixture to acidify the blended product to a pH of 5 or above. The admixture is then vigorously mixed under homogenizing conditions to produce a homogeneous melted and pasteurized imitation cheese product.
U.S. Pat. No. 3,922,374 to Bell et al. discloses the preparation of an imitation cheese from acid casein by forming calcium or sodium casinate in-situ. A formulation containing water and acid casein is prepared to which sodium hydroxide or calcium hydroxide is added. Fat is added to the formulation as well as other ingredients, such as emulsifying salts. The final product contains sufficient acid to achieve a product pH of about 5. The Bell et al. patent, however, does not recognize or provide any method for removing stale flavors from acid casein.
U.S. Pat. No. 4,444,800 to Bixby et al. is directed to a method for the manufacture of a simulated cheese product that is prepared from dry, particulate rennet casein. The imitation cheese product is prepared by mixing particulate rennet casein and an edible solvation agent with water. The solvation agent is substantially similar to emulsifying salts normally used in the preparation of process cheese. A fat or an oil is blended into the admixture of rennet casein and solvation agent and sufficient quantities of flavoring agents and acidulants are added to impart the desired product flavor and pH. The mixture so formed is agitated under high sheer at a temperature of about 190.degree. F. to 205.degree. F. and is maintained at this temperature with sufficient severity of sheering agitation for a time period of two to four minutes to solvate the rennet casein that is present and to provide a plastic body to the simulated cheese product. The Bixby et al. patent also does not recognize the problems associated with stale flavors in rennet casein.
While various methods are known for producing imitation cheese from acid casein and rennet casein, it would be desirable to provide a simple and economical process for removing stale and off flavors from acid casein and rennet casein prior to using the acid casein or rennet casein in the manufacture of an imitation cheese product.
Accordingly, it is an object of the present invention to provide a method for the manufacture of imitation cheese from acid casein or rennet casein wherein the stale and off flavors of acid casein or rennet casein are removed prior to manufacture of the imitation cheese product.
It is another object of the present invention to provide a method for removing stale and off flavors from acid casein and rennet casein prior to the use of the acid casein and rennet casein in the manufacture of food products, such as imitation cheese.
These and other objects will become more apparent from the following detailed description.